The analysis of major industrial accident databases indicates that lightning events are the most frequent cause of technological accidents triggered by natural events in chemical and process plants. Severe fires, mainly affecting storage farms, are the most frequent final scenario associated to such events. In the present study, a quantitative methodology for the assessment of the risk due to major accidents triggered by lightning is presented. The methodology was developed within a common framework for the quantitative assessment of risk due to external hazard factors in chemical and process plants. The procedure also allows the identification of the credible scenarios that may be associated to the different modes of structural damage and the identification of critical equipment items.